1. Field of the invention:
This invention relates to a V-ribbed belt having a plurality of ribs on a belt base along the lengthwise direction of belt and the method of manufacturing the same.
2. Description of the prior art:
The V-ribbed belt having a plurality of ribs on a belt base along the lengthwise direction of belt is already known. Such a V-ribbed belt is used as transmission belt, for example, it is used in a household drier as it is wound round a rib groove pulley of small diameter and a plain pulley of large diameter (drum).
In the afore-mentioned V-ribbed belt, ribs are usually made of rubber but are not covered with canvas because fitting of canvas on the outer surface of ribs makes it difficult to have ribs project in the manufacturing process of V-ribbed belt. Therefore, in the case of the household drier frictional resistance at the sides of rib becomes large, with the result that abnormal sounds are generated at the start and at the stop of belt running (at the time of overload), at the atmospheric temperature of lower than 0.degree. C. in winter or when the belt running was continued for more than 50 hours. The technique of reducing frictional resistance by mixing short fiber in ribs is also known but this involves lowering of flexuosity and therefore if ribs engage repeatedly with a rib groove pulley of small diameter in the flexed state at a small radius of curvature, ribs crack earlier.
U.S. Pat. No. 3,190,137 discloses a V-ribbed belt having ribs with fiber-flock comprising fine, dense and short fiber, instead of canvas, deposited and adhered onto their outer surface. However, it is difficult technically to adhere fiber uniformly to the outer surface of ribs and this technical difficulty involves the requirement of more number of processes and higher costs, as well as deterioration of quality.